Elements, trace, nutritional importance

Clover analyses are routinely performed for monitoring purposes, mapping and risk assessment. In particular, clover and grass for animal feed are analysed to determine elements of nutritive importance (e.g. Se, Mo) and of potential toxicity (e.g. As, Co). The results of the determination of nutritive elements are used to improve the state of health and growth of domestic animals. Their diet must be well balanced and therefore basic feed often needs to be enriched with respect to trace and major elements. The determination of toxic elements is necessary to avoid health damage to the animals. 

Manganese is a nutritionally important trace element for chicks. Dietary energy and protein sources contain very little bioavailable Mn, and these feed ingredients reduce the biopotency of inorganic Mn supplements. This adverse effect is exerted primarily in the intestine as a result of reduced Mn absorption and is mediated by the fiber and/or ash components of the feedstuffs. Gut absorption efficiencies are higher when a phytate-and fiber-free casein-dextrose diet is fed than when a corn-soybean meal diet is fed. Dietary interrelationships exist between Mn and Co and between Mn and Fe. Cobalt increases Mn absorption and may precipitate Mn toxicosis. Excess dietary Mn reduces Fe utilization, but excess Fe does not affect Mn utilization. Eimeria acervulina infection increases Mn absorption. 

Dang, H.S., Jaiswal, D.D., Nair, S. Daily dietary intake of trace elements of radiological and nutritional importance by the adult Indian population. J. Radioanal. Nucl. Chem. 249,95-101 (2001)... 

Although the identification and analysis of such modifying factors go beyond the scope of trace element analysis, the importance of these factors should be recognized. The complexity of the process that leads from the first step of trace element analysis to the final statement of biological implication necessitates the close collaboration between the analytical chemist and the life scientist. The chemist should not be considered the provider of data, nor the biologist the interpreter of results rather, both scientists must be aware of the whole process—its complexity and its diflBculties (25). Only through this collaboration can the enormous amount of trace element analytical data be put in order and be interpreted properly. On this whole process depends the progress of trace element nutrition research and the improvement of the nutritional status of man. 

Some of the more recent publications about trace elements, trace minerals, or ultratrace elements or minerals, also described as micronutrients, include Micronutrients in Health and Disease Prevention, edited by Adrianne Bendich and C.E. Butterworth Trace Elements in Nutrition of Children, edited by Ranjit Kumar Chandra and Trace Elements, Micronutrients and Free Radicals, edited by Ivor E. Dreosti. The latter reference raises the important question of the undesirable health effects of the chemical agents called free radicals, and their control or eradication by such vitamins as E, C, and beta-carotene. There is a history of the health effects of trace elements going back to Henry A. Schroeder, who in the early 1970s wrote Trace Elements and Man Some Positive and Negative Aspects and also The Poisons Around Us Toxic Metals in Food, Air, and Water. Even further back there was Karl... 

Reflect and Apply Biologically and nutritionally important trace elements tend to be metals. What is their likely biochemical function ... 

The classification of the essential minerals into major elements and trace elements depends upon their concentration in the animal or amoimts required in the diet. Normally trace elements are present in the animal body in a concentration not greater than 50 mg/kg and are required at less than 100 mg/kg diet. Those essential mineral elements that are of particular nutritional importance together with their approximate concentrations in the animal body are shown in Table 6.1. 

In 1971 it was reported that a significant growth effect, in rats maintained on purified amino acid diets in a trace-element-free environment, was obtained when the diets were supplemented with tin. These studies suggested that tin was an essential trace element for mammals. The element is normally present in foods in amounts less than 1 mg/kg DM, the values in pasture herbage grown in Scotland, for example, being of the order of 300-400 pg/kg DM. The nutritional importance of this element has yet to be determined, but it is suggested that tin contributes to the tertiary structure of protein or other macromolecules. Tin is poorly absorbed... 

As already mentioned, the ultra trace elements other than selenium and iodine are a disparate group in terms of their possible requirement or nutritional importance for human health and well-being. Although molybdenum has known essential functions, it has no unequivocally identified practical nutritional importance. The other 14 ultratrace elements discussed here have been suggested to be essential based on circumstantial evidence. This evidence is presented below along with some indication of possible requirement (extrapolated from the deficient animal intakes shown in Table 3), and some indication as to what constitutes a high intake. 

The importance of the basal medium in culturing normal cells was demonstrated by Dr. Richard Ham (Ham and McKeehan, 1979). Dr. Ham s laboratory developed a number of different types of culture media, in which the concentrations of the individual nutritional components have been optimized to support the growth of specific types of normal, differentiated cells. The most widely used is nutrient mixture FI2, which contains nonessential, as well as essential, amino acids, a number of lipids, and trace elements (Table 5). 

PN should provide a balanced nutritional intake, including macronutrients, micronutrients, and fluid. Macronutrients, including amino acids, dextrose, and intravenous lipid emulsions, are important sources of structural and energy-yielding substrates. A balanced PN formulation includes 10% to 20% of total daily calories from amino acids, 50% to 60% of total daily calories from dextrose, and 20% to 30% of total daily calories from intravenous lipid emulsion. Micronutrients, including electrolytes, vitamins, and trace elements, are required to support essential biochemical reactions. Parenteral... 

The need to include a variety of minerals in experimental diets has already been mentioned this was especially stressed (1920-1930) by Boyd-Orr, the director of the Rowett Institute for Animal Nutrition in Scotland. Increasingly refined food sources led to the identification of large numbers of trace elements (e.g., Cu, Mn, Mo, Zn) whose importance in the diet was suggested from hydroponic experiments with plant seedlings. Cobalt is an example of such a trace element. Vitamin Bj2 is synthesized by bacteria in the rumens of sheep and cattle but is absent from their fodder. In Australia, sheep feeding on cobalt-deficient pastures failed to thrive because vitamin B12 could no longer be made. 

Cobalt is an important trace element for proper human nutrition. It is also a natural component of vitamin... 

If vitamins are added to a product to make a nutritional claim, it is critical that shelf-life studies are undertaken to prove that the overages added are sufficient to ensure that the label claims can be met at the end of product shelf life. This is important as none of the vitamins are fully stable in a soft drink environment and some, for instance vitamin C, are very quickly lost in the presence of oxygen. The addition of the fat-soluble vitamins to a soft drink also offers a formulation challenge to ensure that they are fully dispersed and that there are no problems with neck ringing during storage. Trace metals, particularly the transition elements, can also have a deleterious effect on vitamin shelf life, and sometimes metal scavengers, such as EDTA or phosphate salts, are added to improve the shelf life. 

Deficiency syndromes of Zn, Cu, Cr, Se and Mo have occurred in patients on total parenteral nutrition (TPN). There is still much research to be done in assessing the nutritional status of many elements and understanding their metabolism, so that normal dietary intake may be supplemented for health benefits. Table 2 is a summary of the amounts required, the functions and the nutritional (usually dietary) imbalances in humans, where known, of the essential trace elements.31-33 (Note that this summary does not attempt to include imbalances related to environmental toxicology and occupational hazards.) Several trace elements have important functions in the immune system. Some are associated with nucleic acid. Others have structural roles, such as Si in cartilage, F and Zn in bone. They may be parts of vitamins, such as Co in vitamin B12, or hormones, such as iodine in thyroid hormones, Zn and Cr have a role in the synthesis and action of insulin.31-33... 

Speciation analysis comes into its own mainly in environmental, nutritional, and biomedical research. The sample matrices are generally highly complex and the requirements for reliable (trace) element determinations are stringent (even for total amounts). The most important challenges in this context involve... 

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